1. Field of the Invention
The present invention relates to a zoom lens and an imaging apparatus. More particularly, the invention relates to a small-sized and high-performance zoom lens having a high zooming ratio, and an imaging apparatus using the zoom lens.
2. Description of Related Art
Digital cameras have been popular, which adopt the following recording system. Namely, the recording system employs, as recording means in the cameras, an imaging device using photoelectric conversion elements, such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal-Oxide Semiconductor). The imaging device forms an object image on a surface thereof, and records the object image by causing the photoelectric conversion elements to convert amounts of light of the object image into electrical outputs, respectively.
Recently, in lens-incorporated cameras, there is a growing demand, among many users, for zoom lenses having a higher zooming ratio.
This is because, unlike a single-lens reflex camera, lenses cannot be interchanged in a lens-incorporated camera, so that if the zooming ratio is low, it is difficult to accommodate various photographic scenes.
Zoom lenses realizing a high zooming ratio have been proposed, e.g., in Japanese Unexamined Patent Application Publication No. 2003-287681 (Patent Document 1), Japanese Unexamined Patent Application Publication No. 2005-215385 (Patent Document 2), and Japanese Unexamined Patent Application Publication No. 2007-3554 (Patent Document 3).
A zoom lens described in the Patent Document 1 is constructed by arranging, in the order from an object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a negative refractive power, and a fifth lens group having a positive refractive power. In embodiments thereof, zoom lenses having a zooming ratio of about 10 times are disclosed.
A zoom lens described in the Patent Document 2 is constructed by arranging, in the order from an object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. In embodiments thereof, zoom lenses having a zooming ratio of about 12 times are disclosed.
A zoom lens described in the Patent Document 3 is constructed by arranging, in the order from an object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a positive refractive power, and a fifth lens group having a positive refractive power. In embodiments thereof, zoom lenses having a zooming ratio of some 20 times are disclosed.